1. Field of the Invention
This invention relates to a tractor with a ground-working implement such as a rotary plow drivably and vertically movably coupled thereto.
2. Description of the Related Art
A conventional tractor of the type noted above is disclosed in Japanese Utility Model Publication Kokai No. 60-22103, for example. According to this publication, control valves for controlling hydraulic cylinders are mounted on the upper surface of a lid plate closing an opening formed in the upper surface of a transmission case.
In such a case, a plurality of control valves are arranged on the upper surface of the lid plate of the transmission case. The conventional construction noted above requires hydraulic piping to provide communication among the control valves. Otherwise, the control valves must be directly interconnected to communicate with one another.
Thus, where the control valves are interconnected through hydraulic piping, the conventional construction noted above requires an operation to install the control valves on the lid plate, and an operation to connect the hydraulic piping to the control valves. Where the control valves are interconnected directly, the conventional construction requires an operation to connect the control valves to one another, besides the operation to install the control valves on the lid plate. All these operations render a poor work efficiency of assembling the control valves.
Moreover, when removing one control valve from the lid plate to carry out maintenance, a troublesome operation is required, such as disassembling the hydraulic piping, or disconnecting the control valve from the other control valves. The conventional construction also lacks in facility of maintenance.